2012 Hybrid Yukon Denali major issue. Need help from the experts

[j91z28d1]

so here's that video on the basics of can bus practical troubleshooting. if you have a volt/ohm meter. it would be interesting if you can test for the ohm across the can terminals in the obd2 port. what would tell you if the system is intact.

 

[DGYukon]

ahh, so that's helpful. I was thinking this was from the first event. so we know the Communications Network is still down, so that's not intermittent or one time thing.
since you have that replacement module coming. I hope that fixes it.
there's actually 2 networks, I high speed and a low speed. do you have a ohm meter?

my guess is high speed is down, since you can still see some info from modules besides the ecm. I'd be curious if you can retrieve it those 4 ecm codes and 8 tcm codes.

edit, the 11.9v probably means it sets the codes before the engine even started, at first key on.

Just went out to the truck and it won’t even try to start now. Gives the messages Engine Power is Reduced, Service 4WD and Service Traction Control… scan tool won’t connect either

 

[j91z28d1]

Just went out to the truck and it won’t even try to start now. Gives the messages Engine Power is Reduced, Service 4WD and Service Traction Control… scan tool won’t connect either

I know that sounds bad, but small upside is it's not intermittent. which makes things even harder to find. atleast at this point of you fix it. you know it's fixed.

does the scanner turn on? like it's getting 12v power from the port but can't connect? if so, that's definitely the can bus network down. or the scanner won't turn on. it might be a fuse.

at this point, all I can say fingers crossed it's that rear module like in the video. if not, you might have to get a ohm meter and first step is look for the 60ohms across the 2 pins of the network.



if you take it to a shop, make sure you ask if they have someone good with can bus trouble shooting and is willing to work in hybrids. I've seen stories of towing trucks to places and then finding out they wouldn't touch it.

this tsb shows some of the locations of wiring harnesses routing issues. you might take a look at them for damage in the mean time.